In video coding, for reducing the spatial redundancy of image and fully utilizing the spatial correlation between a given block and the adjacent blocks in a given frame image, the given block is coded based on the prediction result according to the adjacent blocks. Typically, the prediction result is obtained according to the sequence of the upper-left, left and upper blocks relative to the given block. Because the upper-left, left and upper blocks have been processed before the given block, the bit rate can decrease by directly coding the difference between the predicted value and the actual value.
Due to the pixel blocks have a matrix form and accordingly the associated residual coefficients have a two-dimensional array form, the two-dimensional residual coefficient are required to be converted into a one-dimensional series and then performed by the entropy coding and thereby achieving the compression. In the intra frame prediction encoding process, the compression efficiency of the entropy coding is related to the arrangement characteristic of the one-dimensional residual coefficient series. Specifically, the compression will have a relatively-high efficiency if the nonzero residual coefficients are mainly located in the front part of the one-dimensional residual coefficient series; alternatively, the compression will have a relatively-low efficiency if the nonzero residual coefficients are located randomly in the one-dimensional residual coefficient series, and accordingly the corresponding bit rate is relatively high.